Electric temperature regulator

ABSTRACT

A thermostat for a refrigerator has a pair of substantially parallel bimetallic elements exposed to the atmosphere of the refrigerator compartment and adapted to bend in opposite directions on temperature variation. Attached to the free end of one of the strips is an elongated element which carries a contact engageable with a fixed contact to close a circuit that operates the refrigerator compressor. Extending between the free end of the other strip and the movable contact is a leaf spring. Both of the free ends move in opposite directions with one of these free ends traversing a line extending from the other free end to the movable contact, thereby forming a toggle linkage for snapping the contacts open and closed, depending on the direction of temperature change.

United States Patent [1 1 Schiiller [451March 20, 1973 [5 1 ELECTRIC TEMPERATURE 2,236,699 4/1941 Riche ..337/343 REGULATOR 2,189,996 2 1940 Riche... .200/67 D x 2,170,748 8/1939 Eaton ..337/345 [76] Inventor: Peter Schuller, WiIhelm-Raabe-weg 4A, 3006 Grossburgwedel, Ger- FOREIGN PATENTS OR APPLICATIONS many 626,486 2/1936 Germany 2337/1 1 1 [22] Filed: June 8, 1970 Appl. No.: 44,530

Related U.S. Application Data Continuation-impart of Ser. No. 736,087, June 11, 1968, Pat. No. 3,525,222.

U.S. Cl. ..337/335, 337/343, 337/345,

337/379 Int. Cl. ..HOlh 37/52 Field of Search ..200/67 D; 337/38, 95, 111,

Primary ExaminerRoy N. Envall, Jr. Att0rney-Karl F. Ross 5 7 ABSTRACT A thermostat for a refrigerator has a pair of substam tially parallel bimetallic elements exposed to the atmosphere of the refrigerator compartment and adapted to bend in opposite directions on temperature variation. Attached to the free end of one of the strips is an elongated element which carries a contact en gageable with a fixed contact to close a circuit that operates the refrigerator compressor. Extending between the free end of the other strip and the movable contact is a leaf spring. Both of the free ends move 1 in opposite directions with one of these free ends traversing a line extending from the other free end to the movable contact, thereby forming a toggle linkage for snapping the contacts open and closed, depending on the direction of temperature change.

3 Claims, 5 Drawing Figures PATENTEDHARZOIQB I 57211937 4 FIG. 5

Pefer SchU/Ier INVENTOR.

Attome y ELECTRIC TEMPERATURE REGULATOR CROSS-REFERENCE TO COPENDING APPLICATION This is a continuation-in-part of of my copending application Ser. No. 736,087 filed on June ll I968 (now US. Pat. No. 3,525,222 issued Aug. 25 1970).

FIELD OF THE INVENTION The present invention relates to an electric temperature regulator, more especially but not exclusively for refrigerators and the like.

BACKGROUND OF THE INVENTION Refrigerators are generally regulated in such a way that the temperature of the evaporator is the sensed controlling parameter. For this purpose a sensitive element, connected via a line to a container which is subdivided into two chambers by a diaphragm, is in contact with the evaporator. The chamber communicating with the line, the line and, sometimes, the sensitive element are filled with a suitable liquid or gas. A plunger which actuates a switch contact is connected to the diaphragm.

Temperature regulators of this kind are complicated to construct and expensive to manufacture. The reason for this lies in particular in the rods, levers or other mechanisms by which the very small movements of the switch contact connected to the diaphragm have to be converted into switch movements suitable for achieving control.

Furthermore, it is known to provide electric temperature regulators for electric heating apparatus and the like in which, actuation of a switch knob serves to deflect a bimetal tongue which is connected to an elastic spring and on whose one end a switch contact is arranged. In the on position this switch contact abuts against an associated switch contact, whereby the circuit containing the electric heating apparatus is closed.

OBJECTS OF THE INVENTION It is, therefore, an object of the present invention to provide an improved electrical temperature regulator.

Another object is to provide a thermostat which gives fast and trouble-free operation, while being simple to manufacture.

SUMMARY OF THE INVENTION l attain the above objects, in accordance with a feature of this invention, with a thermostat comprising a pair of substantially parallel and coplanar bimetallic strips each having a free end and adapted to bend in opposite directions on temperature variation, c.g. away from each other on heating, toward each other on cooling. An elongated element is attached to one of the free ends and carries a contact which is engageable with another contact. One of the free ends defines a straight line with a location along the element remote from the free end of the one of the strips. A spring is connected to the element at the location and to the free end of the other strip at a junction which traverses the line as the other strip deforms. The toggle-like action of this spring snaps the contacts open or closed, depending on whether the strips are being heated or cooled.

Since both strips deform simultaneously in opposite directions, the dead-center position of the thermo stat-when the two ends of the spring and the free end of the strip carrying the element are all in line--exists only for a very brief instant as the two strips pull away from or cross each other. As soon as this instantaneous dead-center position is passed, the toggle action of the spring displaces the contact to drive it well out of line with the two free ends of the strips, thereby reinforcing the movements of the strips. The thermostat can be counted on to snap from one position to the other at a very exact instant, and the difference between the temperature at which it snaps on cooling will be only slightly removed from that on heating, the two changeover points being therefore much closer than has heretofore been possible. What is more, the contacts are pushed together rather strongly so that they can be used to carry a relatively large amount of current without fear of damaging them.

According to a further feature of this invention one of the strips is substantially U-shaped, with the ends of its U-legs clamped in a support, and the other strip is shorter and flanked by these legs. This other strip is formed on its free end with a bend-down tab whose lower edge is connected to one end of the leaf spring which extends back toward the support and bears against the contact, the spring always being stressed to some extent. The element carrying the movable contact is elongated and has one end attached to the U- base and also extends back toward the support. Thus, the lower edge of the tab, the movable contact, and the U-base define the three points which form the pivots of the toggle mechanism, with the tab lower edge being the middle point and being displaceable across a line extending between the other two points. It would of course be possible for the points to be arranged otherwise, it being only important here that no one of them is stationary. In virtually all prior-art toggle mechanisms, at least one point is stationary.

In accordance with a further feature of the invention associated with the bimetal elements, there is a heat source which is adapted to generate heat in the open condition of the two switch contacts but which is inoperative in the closed condition of the two switch contacts.

An electric heating spiral, an ohmic resistor or an incandescent lamp may serve as the heat source.

In accordance with a further feature of the invention, an electric heat source designed as an ohmic resistor may be mounted in a fingered saddle-like support.

The heat source, which is in operation during the stoppage of the compressor of the refrigeration unit, simulates a need for refrigeration, so that the electric temperature regulator switches and the compressor is started up thereby in such a way that at all times an average temperature of, for example, about -5C is maintained in the evaporator freezer compartment.

DESCRIPTION OF THE THE DRAWING One representative embodiment of an electric-temperature regulator in accordance with the invention will be described in greater detail hereinafter, with reference to the accompanying diagrammatic drawin in which:

FIG. 1 is a sectional elevation of an electric temperature regulator in accordance with the invention;

FIG. 2 is a top plan view of a bimetal element of the electric temperature regulator of FIG. 1;

FIG. 3 is a top plan view of a mounting for an ohmic resistor included in the electric temperature regulator of FIGS. 1 and 2; and

FIGS. 4 and show a detail of FIG. 1, in two alternative positions.

SPECIFIC DESCRIPTION The illustrated electric temperature regulator comprises bimetal elements 1 and 2. This element or tongue 1 incorporates a flexible spring blade 3 having a switch contact 4 mounted on its free end. Associated with the switch contact 4 there is a switch contact 5, which is mounted on a terminal lug 6. The switch contact 5 is supported by by electrically insulating spacers 7 preferably consisting of ceramic disks and forming a support for the strips 1 and 2.

A mounting strap 8 is combined with the insulation 7, the bimetal elements 1, 2, and the terminal lug 6 into a single constructional unit by a tubular rivet 9. This mounting strap 8 is traversed by a rotary spindle 10 terminating at its lower end in a plunger 11 which confronts the strip 2. A switch knob 12, by which the desired temperature in the main freezer compartment can be set, is connected to this spindle.

In accordance with an essential feature of the invention, the bimetal elements 1, 2 co-operate with a heat source which is in operation in the open condition of the two switch contacts 4, 5 but which is inoperative in the closed condition thereof. The expression heat source is to be understood in the widest sense of the word. For example, an electric heat source in the form of an electric heating spiral or an incandescent lamp can be used for this purpose. In the case of the embodiment illustrated in the drawing an ohmic resistor 13, which lies adjacent or in the vicinity of the bimetal elements 1, 2, serves as the heat source. This ohmic resistor 13 is mounted in a fingered saddle-like support 14 (FIG. 3).

The mounting support 14 comprises three fingers or tongues, of which the two external tongues engage the ohmic resistor 13 from below whereas the central tongue engages same from above. The resistor 13 is connected via leads 15, 16 with two electrical terminal lugs 6, 17. As is evident from FIG. 1, the fingered support 14 is clamped between the tab 6 and the bottom spacer 7.

The front end of the tab 17 is designed as a stop for the contact 4; current is supplied to the electric temperature regulator via electrical connections 18, 19.

The electric temperature regulator shown in FIG. 1 has a housing 20 provided with slots 21 opening into the main compartment of the refrigerator served by the system.

Rotation of the switch knob 12 serves to vary the deflection of the element 2 and thereby also the instant at which the regulator will switch on. When the switch contacts 4, 5 are in the open condition, so that the compressor of the refrigeration unit is out of operation, the ohmic resistor 13 is energized. By this means, a need for refrigeration is simulated which causes the electric temperature regulator to switch and actuates the compressor so that the heat removal is resumed. Thus it is ensured that, despite the location of the electric temperature regulator in the main freezer compartment, an

average temperature of, for example, about 5C is maintained in the evaporator freezer compartment.

FIGS. 4 and 5 show the bimetallic strips 1 and 2 in their two different positions. The position shown in FIG. 1 is a dead-center one which they only assume in stantaneously as they cool.

The strip 2 has on its free end a bent-over tab 2a with a lower edge 2b from which extends a prestressed leaf spring 3a whose other end bears against the contact 4. A compression or other type of spring would be equally usable. The strip 1 has a free end la that is connected to the flexible conductive element formed by spring 3 which extends straight to the contact 4 and is formed with a central cutout 3b (see FIG. 2) allowing passage of the strip 2 and spring 3a.

Thus, as shown in FIG. 4, when the strips 1 and 2 are heated the strip 2 bends upwardly and the strip 1 downwardly so that the edge 2b lies above the element 3 and the spring 3a in toggle-fashion forces the contact 4 down against the contact 5.

FIG. 5 shows how, as the unit cools, the strip 2 moves downwardly and the strip 1 upwardly so that the edge 2b drops below the element 3 and the spring 3a pushes the contact 4 up and away from the contact 5.

In both cases the opening and closing of the contacts 4, 5 takes place very quickly. Once the edge 2b traverses the straight line between the contact 4 and end In, the toggle action immediately displaces the contact 4 in a direction opposite to that of the deflection of the strip 2. A very clean switching is thereby obtained, since the crossover time for the edge 2b is very short due to the fact that both elements 1 and 2 always deflect in opposite directions under the same thermal conditions.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

I claim:

1. A thermostat comprising: v

a support having a plurality of stacked insulation disks; p

a pair of normally coplanar bimetallic strips mounted on said support between a pair of said disks and extending therefrom in substantially the same direction, said strips having respective free-end regions deflectable in opposite directions upon temperature variation to opposite sides of a common plane, one of said strips being of U-shaped configuration with a bight remote from the support and a pair of legs extending from said bight to said support, the other of said strips lying between said legs and reaching from said support to terminate short of said bight;

a first electrical contact mounted on said support between another pair of said disks adjacent said strips;

an elongated flexible element extending from the bight of said one of said strips to a position adjacent said first contact and carrying a second contact overhanging and engageable with said first contact to form therewith a closed electrical control circuit, said free end of said other of said strips projecting transversely to said flexible element through a window formed by saidv legs and said bight, said element being supported only by said either side of said line wherein said contacts enone of said strips adjacent to said free end; and gage and are disengaged respectively bowed Spring connected to Said element at Said 2. The thermostat defined in claim 1 whereby said second Contact and to the transversely'projecting element is substantially straight and flexible and lies on free-end region of said other strip at a junction 5 Saidline trasversing a line connecting said free end of said one strip with said second contact upon predetermined change in the temperatures of said strips, said junction having stable positions on 3. The thermostat defined in claim 2 wherein said spring is a leaf spring. 

1. A thermostat comprising: a support having a plurality of stacked insulation disks; a pair of normally coplanar bimetallic strips mounted on said support between a pair of said disks and extending therefrom in substantially the same direction, said strips having respective free-end regions deflectable in opposite directions upon temperature variation to opposite sides of a common plane, one of said strips being of U-shaped configuration with a bight remote from the support and a pair of legs extending from said bight to said support, the other of said strips lying between said legs and reaching from said support to terminate short of said bight; a first electrical contact mounted on said support between another pair of said disks adjacent said strips; an elongated flexible element extending from the bight of said one of said strips to a position adjacent said first contact and carrying a second contact overhanging and engageable with said first contact to form therewith a closed electrical control circuit, said free end of said other of said strips projecting transversely to said flexible element through a window formed by said legs and said bight, said element being supported only by said one of said strips adjacent to said free end; and a bowed spring connected to said element at said second contact and to the transversely-projecting free-end region of said other strip at a junction trasversing a line connecting said free end of said one strip with said second contact upon a predetermined change in the temperatures of said strips, said junction having stable positions on either side of said line wherein said contacts engage and are disengaged respectively.
 2. The thermostat defined in claim 1 whereby said element is substantially straight and flexible and lies on said line
 3. The thermostat defined in claim 2 wherein said spring is a leaf spring. 